Surgery after Stage IV diagnosis???

I was diagnosed in November 2016, Stage IV with several mets to liver. (HER-2 +++) I've had 7 rounds of Taxol, Herceptin and Perjeta and will continue on the Herceptin and Perjeta indefinitely at this point. My latest CT show shows 1 suspected small spot remaining on my liver. I will have a PET scan in July to see where we are.

My question is, how many of you in a similar situation have had a mastectomy after treatment? My oncologist first said he would send me on to a surgeon, but I've also seen another onc who specializes in just breast cancer and she recommended NO surgery. She said it wouldn't make any difference since the cancer had already spread from the breast. I do understand what She is saying, but what if there is still cancer in the breast that is not detected on the scans??

Any advice or experience stories are appreciated!Thanks!